A typical surgical stapler apparatus comprises a handle at a proximal end and two elongated jaw-like members at the distal end, joined together at a hinge. The jaw-like members articulate to open and close to capture tissue between the jaw-like members. The user controls the device from the handle to open and close the jaw-like members, actuate deployment of staples and in general manipulate and control the device. One of the jaw members carries a cartridge containing staples arranged in one or more rows. The other one of the jaw-like members comprises an anvil surface against which the staples are driven to deform the staple legs. Staples are driven out of the cartridge by a caming surface or slider that moves longitudinally against a plurality of laterally positioned pushers that push each staple out of the cartridge. The caming surface of the slider is angled to compliment the angular surface of the pushers. Some staplers include a blade that follows the caming surface so as to cut the tissue between the two or more rows of delivered staples.
Surgical staplers are used in a variety of surgical techniques including laparoscopic and/or endoscopic or other minimally invasive surgical procedures in which the stapler is inserted through a cannula or tube positioned within a small incision in a patient's body. In laparoscopic minimally invasive surgery, a trocar is inserted across body tissue of a patient to access a body cavity and to create a channel for the insertion of a camera, such as a laparoscope. The camera provides a live video feed capturing images that are then displayed to the surgeon on one or more video monitors. Additional trocars are inserted to create additional pathways through which surgical instruments, including surgical staplers, can be inserted for performing procedures observed on the video monitor. The targeted tissue location such as the abdomen is typically enlarged by delivering carbon dioxide gas to insufflate the body cavity and create a working space large enough to accommodate the scope and instruments used by the surgeon. The insufflation pressure in the tissue cavity is maintained by using specialized trocars having seals that prevent the insufflation gas from escaping and collapsing the surgical working space. Laparoscopic surgery offers a number of advantages when compared with an open procedure. These advantages include reduced pain and blood loss and shorter recovery times.
As laparoscopic surgery evolves to become even more minimally invasive with incisions and trocar/cannula diameters becoming smaller and smaller, surgical staplers for use in laparoscopic, minimally invasive procedures must be designed to fit within the small lumen of a cannula. Generally, a surgical stapler is inserted into a cannula with the jaw-like members in a closed orientation until the device jaws are inside the patient where the jaw-like members are opened to grasp and staple tissue. The handle of the stapler resides outside of the patient in control of the surgeon user. A portion of the shaft of the stapler between the jaw-like members and the handle is long enough to extend from outside the patient to inside the patient. During the stapling procedure, the elongate shaft of the stapler resides inside the cannula into which it was inserted.
The distal jaw-like members include many components such as an anvil for forming staples, a staple cartridge with a plurality of staples, a caming surface, a slider, pushers, a blade and other components which must all be small enough to fit through a small diameter cannula and made to function reliably and repeatedly from outside the patient. As shown in FIG. 1A, when closed, the distal jaw-like members of the surgical stapler 2a have a substantially circular cross-section wherein approximately one half of the cross-section comprises the lower jaw 3a that houses the staples 7a. Approximately a little less than the other half of the cross-section comprises the upper jaw 4a that houses the anvil. The circular cross-section of the distal jaw includes a gap 5a between the upper and lower jaws for receiving tissue to be stapled. In FIG. 1A, a vertical line 6a divides the cross-section in half and represents a blade line or an I-beam that carries a blade to cut tissue between one or more rows of staples 7a. The I-beam slides longitudinally along the length of the distal end and also functions to push the staples 7a out of the lower jaw 3a, across the gap 5a and against the anvil of the upper jaw 4a. A plurality of vertical lines 7a in FIG. 1A represent three rows of vertically arranged staples 7a residing in the lower jaw 3a on either side of the blade line 6a. The conventional stapler design involves ejecting the staples perpendicularly against the anvil surface.
While conventional laparoscopic staplers are approximately 12 millimeters in diameter, it is desirable to reduce the stapler diameter to fit inside a cannula having a diameter as small as approximately 5-10 mm to provide the patient with a smaller incision, reduced recovery time and reduced scarring. FIG. 1B illustrates a reduced-diameter stapler with the same conventional design as shown in FIG. 1A. As can be seen in FIG. 1B, the smaller stapler 2b has a smaller diameter with less space for a lower jaw 3b and upper jaw 4b. The tissue gap 5b is approximately the same as the tissue gap 5b of the larger stapler 2a for stapling tissue having approximately the same thickness. As a result of the reduced diameter and conventional design that ejects staples perpendicularly against the anvil surface, the smaller stapler 2b accommodates staples 7b in the lower jaw 3b that have shorter staple legs as shown in FIG. 1B. The length SB of the staple legs in the smaller variation of FIG. 1B is significantly shorter than the length SA of the staple legs in the larger variation of FIG. 1A. This is an inherent limitation of staple leg length in smaller diameter staplers employing the same conventional design. Hence, it is desirable to have a smaller diameter stapler that is capable of being inserted into smaller cannulas while at the same time still retaining the same ability to fire larger staples.
FIG. 2A illustrates tissue 8a that has been cut along a blade line 6a and stapled with the conventional stapler 2a of FIG. 1A. FIG. 2A shows three rows of staples 7a delivered into tissue 8a adjacent to a blade line 6a. The other three rows of staples 7a on the opposite side of the blade line 6a are delivered into a tissue segment that is not shown in FIG. 2A. The distance CA is the length of tissue 8a that has been stapled. FIG. 2B illustrates tissue 8b that has been cut along a blade line 6b and stapled with the conventional stapler 2b of FIG. 1B having a smaller diameter relative to the stapler of FIG. 1A. FIG. 2B also shows three rows of staples 7b delivered into tissue 8b adjacent to the blade line 6b. The distance CB is the length of tissue 8b that has been stapled. When compared with the length CA of FIG. 2A, the smaller diameter stapler 2b produces a shorter length CB. The length CB is naturally shorter as staples 7b are more closely placed in the reduced lower jaw 3b area.
Also, the cuff length, which is the distance between the blade line or cut edge and the closest staple row to the cut edge or blade line, may be shorter as longer staples are placed closer to the diameter as shown in FIG. 2B when compared to FIG. 2A. In order to fit multiple rows of staples 7b in a smaller diameter version stapler 2b, the stapler 2b is configured to deliver a row of staples 7b as close as possible to the blade line 6b as shown in FIG. 2B. The proximity of this line of delivered staples 7b is much closer to the blade line 6b than the same line of staples 7a in the larger version stapler 2a. Proximity of staples to the blade line 6b may increase the chances of a misfired staple crossing the blade line. Also, proximity of the staples to the blade line results in the first line of staples 7b being very close to the edge of the tissue 8b which may reduce tissue holding. Hence, it is desirable to provide a smaller stapler that reduces the risk of staple jamming and that provides more tissue between the staple line and the edge of tissue.
In order to accomplish the above-mentioned objectives, a smaller diameter stapler utilizing a conventional design may require that the design includes shorter staples or other design compromises. Hence, it is desirable to have a smaller stapler without sacrificing the above-mentioned objectives while at the same time retaining the same functionality and efficacy in a design with smaller diameter.
Also, many other factors enter the equation for an improved stapler. These factors include but are not limited to reducing the force required to deliver staples. Reducing the actuation force improves the accuracy for the surgeon requiring finesse in a surgical procedure and also reduces surgeon fatigue. Typically, when staples are fired perpendicularly against an anvil surface, the staple legs are forced to buckle. Another factor that creates a better stapler is the strength of the deformed staple. For instance, the deformed staple must have a shape that includes a space for receiving tissue without unduly compressing or severing the tissue in the location of the staple. Also, the deformed shape of the staple must be strong enough to withstand forces that would tend to pull the staple open. Overall, it is an object of the present invention to provide an improved stapler that retains the functionality and efficacy in a reduced-diameter stapler and resulting staple line taking into consideration the above-mentioned as well as other design factors. Conversely, it is an object of the present invention to provide a stapler having the same diameter as a conventional surgical stapler that can fire longer staples with circumferential firing than previously possible without circumferential firing.